1. Field of the Invention
The present invention relates to a resin composition comprising an N-alkyl-substituted maleimide/olefin copolymer and a specified resin, which has excellent heat resistance, rigidity, izod impact strength, weather resistance and dimensional resistance.
2. Description of the Related Art
Recently, various high-performance resins have been actively developed with progress of the polymer-alloying technology. This development have rapidly enabled us to plasticize materials which had not been applied. In particular, the plasticization has intensively studied in the field of the automobile, electric and electronic industries and, for example, the plasticization of the automobile body which has been made up by steels is studied. Although the alloy of polycarbonates and ABS has been once adopted, there are problems on productivity, color tone and the like because the alloy with poor heat resistance is coated off-line.
GE Company has developed an alloy of a polyamide and a polyphenylene oxide. Although this material has improved water absorption properties as well as changes in dimension and physical properties compared with the polyamide itself, there are many problems of insufficient physical properties, as well as low rigidity, poor weather resistance and the like which derive from some defects of amides.
Having low weather resistance and other good physical properties, polyesters such as a polybutylene terephthalete have been studied to blend with a variety of resins such as a polyphenylene oxide, a polycarbonate and an elastomer. However, these blending does not provide the resins with satisfactory, combined properties of heat resistance, rigidity, izod impact strength and the like.
On the other hand, maleimide copolymers with large heat resistance have been studied for various methods of blending. For example, a method in which methyl methacrylate is copolymerized with an N-aromatic-substituted maleimide is disclosed in Japanese Patent Publication No. 43-9753, Japanese Patent Laid-Open Nos. 61-141715, 61-171708 and 62-109811; and a method in which styrene resins are copolymerized with an N-aromatic-substituted maleimide is disclosed in Japanese Patent Laid-Open Nos. 47-6891, 61-76512 and 61-276807. Although the resins obtained by these methods, however, have larger heat resistance with the increased content of N-aromatic-substituted maleimides, there are problems that they are very fragile, poor in processability and colored easily. Thus these N-aromatic-substituted maleimides are only blended in a small amount as heat resistance modifiers to acrylonitrile/butadiene/styrene (ABS) resin.
For prevention of decrease in mechanical strength of the resins by increasing maleimide units, for example, a method for graft-polymerizing phenylmaleimide and styrene to rubber-like material, or a method for kneading them with rubber-like material is described in, for example, Japanese Patent Laid-Open Nos. 58-206657, 59-11322 and 59-49255. Since the heat resistance and rigidity of the resins was decreased by introducing rubber components using these methods to increase their izod impact strength, it is difficult to satisfy the heat resistance, izod impact strength and rigidity at the same time. Further, use of the resins with light color is limited because of coloring molded objects. Compositions of such materials and polyamide resins are also described in Japanese patent Laid-Open Nos. 62-59647 and 62-179546, thought it was also difficult to satisfy the heat resistance, izod impact strength and rigidity of them at the same time.
Although N-alkyl-substituted maleimide/olefin copolymers are interesting polymers which have the properties such as good heat resistance and weather resistance, high rigidity, and practical mechanical strength, it is desired to further improve the izod impact strength of the resins, and improvement of changes in physical properties and change in dimension by water absorption is also desired. Further, Japanese Patent Publication No. 49-12576 describes a resin composition of maleimide-olefin compound, a simple blend, is not made up by a reaction (interaction), so that it is improved a little for flexural stiffness and izod impact strength.